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  <xsd:element name="EffectiveIncomeTaxRateReconciliationDeferredTaxTrueUpAdjustmentAmount" id="mrkr_EffectiveIncomeTaxRateReconciliationDeferredTaxTrueUpAdjustmentAmount" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="EffectiveIncomeTaxRateReconciliationDeferredTaxTrueUpAdjustmentPercent" id="mrkr_EffectiveIncomeTaxRateReconciliationDeferredTaxTrueUpAdjustmentPercent" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="CancerPreventionAndResearchInstituteOfTexasGrantAgreementMember" id="mrkr_CancerPreventionAndResearchInstituteOfTexasGrantAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="GrantAgreementPaymentsRequiredPercentageOfNetSalesToGrantsReceived" id="mrkr_GrantAgreementPaymentsRequiredPercentageOfNetSalesToGrantsReceived" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="GrantAgreementRevenueSharingPercentageRemainderOfRevenueTerm" id="mrkr_GrantAgreementRevenueSharingPercentageRemainderOfRevenueTerm" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="BaylorCollegeOfMedicineLicenseAgreementMember" id="mrkr_BaylorCollegeOfMedicineLicenseAgreementMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="SaleOfStockValueOfSharesIssuedInTransaction" id="mrkr_SaleOfStockValueOfSharesIssuedInTransaction" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="LicenseAgreementMaximumMilestonePaymentsAgreedToBePaid" id="mrkr_LicenseAgreementMaximumMilestonePaymentsAgreedToBePaid" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="LicenseAgreementLiquidityIncentivePaymentPercentage" id="mrkr_LicenseAgreementLiquidityIncentivePaymentPercentage" type="dtr-types:percentItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="StockAndWarrantsIssuedDuringPeriodSharesNewIssues" id="mrkr_StockAndWarrantsIssuedDuringPeriodSharesNewIssues" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="StockAndWarrantsIssuedDuringPeriodValueNewIssues" id="mrkr_StockAndWarrantsIssuedDuringPeriodValueNewIssues" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="ProceedsFromIssuanceOfCommonStockAndWarrantsNet" id="mrkr_ProceedsFromIssuanceOfCommonStockAndWarrantsNet" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="debit" />
  <xsd:element name="MasterServicesAgreementTerm" id="mrkr_MasterServicesAgreementTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="PreFundedWarrantMember" id="mrkr_PreFundedWarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="PrivatePlacementWarrantMember" id="mrkr_PrivatePlacementWarrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="EquityIncentiveAward2024Member" id="mrkr_EquityIncentiveAward2024Member" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="NationalInstitutesOfHealthSmallBusinessInnovationResearchForPancreaticCancerMember" id="mrkr_NationalInstitutesOfHealthSmallBusinessInnovationResearchForPancreaticCancerMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="AdditionalCpritGrantMember" id="mrkr_AdditionalCpritGrantMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantedInPeriodWeightedAverageRemainingContractualTerm" id="mrkr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantedInPeriodWeightedAverageRemainingContractualTerm" type="xbrli:durationItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="ClassOfWarrantOrRightNewIssuance" id="mrkr_ClassOfWarrantOrRightNewIssuance" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
  <xsd:element name="AtMarketOfferingMember" id="mrkr_AtMarketOfferingMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="SeriesBWarrantsMember" id="mrkr_SeriesBWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="SeriesaWarrantsMember" id="mrkr_SeriesaWarrantsMember" type="dtr-types:domainItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="true" />
  <xsd:element name="PaymentsOnTerminationOfAgreement" id="mrkr_PaymentsOnTerminationOfAgreement" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" xbrli:balance="credit" />
  <xsd:element name="RecentlyIssuedAccountingStandardsAdoptedPolicyTextBlock" id="mrkr_RecentlyIssuedAccountingStandardsAdoptedPolicyTextBlock" type="dtr-types:textBlockItemType" substitutionGroup="xbrli:item" nillable="true" xbrli:periodType="duration" abstract="false" />
</xsd:schema>
